<b>Development of a C-terminal-region-specific radioimunoassay of parathyroid hormone-related </b><b>protein </b>

Abstract

Few data are published regarding the molecular forms or concentrations of circulating and urinary parathyroid hormone-related protein (PTHrP) in normal subjects and patients with humoral hypercalcemia of malignancy (HHM). We have developed a C-terminal-regionspecific radioimmunoassay for human PTHrP] 09-141 (C-PTHrP radioimmunoassay) using a sheep antiserum immunized with a novel synthetic human PTHrP109-141 for immunogen and a novel synthetic [Tyr'08]PTHrP108-14] for radiolabel. The detection limit of this assay is 2 pM for human PTHrP109-141 and is sensitive enough to detect circulating and urinary C-PTHrP in normal subjects. The average immunoreactive concentration of serum (n=76) and urinary (11:12) C-PTHrP in normal subjects are 31.4 iv 7.4 pM and 322.9 i 67.2 pM, respectively. Levels in patients with HHM are significantly elevated when compared to controls. This assay may be useful in the differential diagnosis of hypercalcemia.